In a multistage switching network, some or all switching nodes need a buffer for temporary storage of packets to solve the inconsistency between the transmit rate and the receive rate. However, the capacity of a buffer is limited. Therefore, the backpressure mechanism is often used for input traffic control to avoid packet loss caused by buffer overflow.
Backpressure means that according to the buffer usage, a lower stage node sends backpressure information to an upper stage node, instructing the upper stage node not to send packets until it is instructed to do so. According to the causes of generation, backpressure information can be classified into global backpressure and queue backpressure. When the number of the packets in a buffer reaches or exceeds a certain threshold, global backpressure information is generated. For the purposes of solving problems, the packets in the buffer are queued according to certain rules, to form multiple queues, and in each of the queues, packets are sent in order. When the length of a queue reaches or exceeds a certain threshold, queue backpressure information is generated.
The backpressure transfer and response mechanism in the related art is to send backpressure information among the switching nodes with a buffer stage by stage. In other words, a switching node with a buffer responds to all backpressure information sent by the lower stage switching node, but does not forward such backpressure information to the upper stage switching node.
During the invention, the inventor finds that the related art has at least the following weaknesses:
In the backpressure transfer and response mechanism, a complex internal structure and corresponding processing modules are needed to enable the intermediate stage node in a multistage switching network to respond to all received backpressure information, which raises the design complexity and increases the realization costs.